I826 I ~ ~ g ~ t ~Chemistry, :nic Vol. 14, No. 1, 1975 (2) K. IJiedenzu *lid J. W.Dawson in "The Chemistry of Boron and Its Compounds," E. Muettertics, Ed., Wiley, New York, N. Y., 1967, pp 377-442; G. W. Parshall, ibid.,pp 617-667. (3) T. B. Coyle and F. 6.A. Stone in "Progress in Boron Chemistry," Vol. I, IH. Steinberg and A. L. McCluskey, Ed., Macmillan, New York, N. Y.,1964, pp 83-160. (4) E L Hibbert, Ber. Deut. Chem. Ces., 39, 160 (1906). ( 5 ) F. G. Mann, A. F. Wells, and 0. Purdie, J. Chem. SOC.,l828 (1937); F. G. Mann and A. F.Wells, ibid., 708 (1938). (6) L. H. Long and J. F. Sackman, Res. Coiresp., 8, 523 (1955). (7) M . Halrnann, Speczrochirn. Acta, 16, 407 (1960). (8) 11. G. Kastyanovskii, I. I. Chemin, V. V. Yakshin, and A. W. Stepanyants, Izv. Aked. Nauk SSSR. Ser. Khim.,1629 (1967); Chem. Abstr., $8, 95338 (1968). (9) P. B. Ayscaugh and 1% J. Emeleus, .I. Clzem. Soc., 3381 (1954). (10) M. Siebert, Z . Anorg. Allg. Chem., 273, 161 (1953). (11) W. J. C. Dvke. W. C. Uavies, and W. 9.Jones*9.Gem. Sor., 463 (1930). (12) C. El. Barkord, D.L. k v i , and D. M. Newitf, J. Chem. Soc:, 488
(!?16). (13) F. Ostwald, Z . A n d . Chem., 897, 309 (1963). (14) W .J. Lehmann, 6.0. Wilson, am! I. Sharpiro, J . Chern. Phys., 28.779 (1958). (14) A.Stock and F. Zelder, Ber. Deut. Chent. Ges., 54, 531 (1921). (16) A. D. Noman and W. E. Jolly, Pnog. Syn., 11, 15 (1368). (1'7) R. C. Taylor and A. K. Grimes, Spectrochini. Acta, IQ, 419 (1958). (18) A. Stock and E. Kuss, Ber. Deut. Chem. Ges.. 47, 3113 (1914). (19) T. Wentink and V. H. Tiensuu, J . Chem. Phys., 28, 826 (1958). (20) M. Green and G , A. Martin, Trerts. Fu'araday Soc., 48, 416 (1952). (21) D. A. Daws and G. Bottger, J . Chern. Phys., 34, 689 (1961). (22) E. Pohland and 13. Harlus, Z . Anorg. Allg. Chem., 207, 242 (1932). (23) J. Vanderryn, J . Chem. Phys., 30, 331 (1959).
C.Brown and R. IR.
88, 4390 (1946).
PAll'RICM II'ASSO'IIX,! ROBERT L. KUCZKOWSKI,* PHILIP S. BRYAN, and ROBERT
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Received July 3, i 974 The J = 2 3 and J = 3 4 transitions for eight isotopic species of trinrieZhylan?ine--bor coordinates in the principal axes systems of Me314N.llBM3 and Me314Ne11BD3 were deter method. In combination with previous studies this gave the fallowing structural d(CN) = 1.483 6 0.01 A, LCNB = 109,9 f 1'. Thc dative bond lengths and s were discussed. A dipole moment of 4.84 f 0.1 D was determined for iUe3N-81.13. --y
bond distance in compnnds of the type X3AXr'3 group V, B = group H I elements) is ordinarily expected 60 decrease as the stability to dissociation of the complex increases. A test of this assumption has been recently made for the series (CP-H3)3P*BlI3,2aC E I ~ P H ~ S BH3P.BM392b H~,~~ F3PRH3,3 and fiPH-BN13.4 While t ho1.d for ihe first three compounds, F Although it is less stable than the
(A
=t
Gas-phase struc:tural data have heretofore not been precise enough to permit careful tests of the bond length-stability reiatio~shipfor similar boron--nitrogen adducts. Three trimethylamine adducts have been studied in the gas phase. For (CE33)3N.B(CW3)3, which is readil dissociated, the distance appears to be long ($1.65 ) . 5 For ( C N 3 ) 3 N which is undissociated at room temperature, a value of 1.634 f 0.004 A i s reported.6 For (CH3)3N.BH3, % n ~ i ~ s o c ~but a . t more e ~ stable than (CH3)3Ncussion), there have been three gas-phase structure studies. Am early electron diffraction report gave 1.62 f 0.05 w . 7 haore recent investigations by microwave spectroscopy reported 1.65 $: 0.02 and I .609 A, or 1.637 w,S with preference expressed for the 1,609 A value. The purpose of our investigation was to determine a more asxurate value for the B-N distance in (CGf3)3N.BH3 in order to compare it, with that in (CWjB3N-BF3 and to examine the
x
oc., '78,3,173 (1956). Nu?!. C'henz., 3, 164
e. 'YAY A3640433P
e wreawircc!. The nilrogeri y the doub!e-subsrilution
Inorganic Chemistry, Vol. 14, No. 1, 1975 127
Microwave Spectra of Trimethylamine-Borane Table I. Transition Frequencies Measured for the Isotopic Species of Me,N.BH,
Table 11. Nitrogen and Boron Coordinates and the Nitrogen-Boron Bond Distance Species' J+J' ZN,b A Zg,b A d(B-N), A
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No.
Transitipn Species
J-tJ
1
Me,14N.11BH3 2 -+ 3
2
Me,l'N."BH,
3
Me,14N."BH3
4
Me,15N.'oB€I,
5
Me3'4N.11BD3
6
Me,1SN.L1BD3
7
Me,14N."BD3
8
Me,'5N.'oBD,
3 +4 2 +3 3+4 2 -t 3 3 -+ 4 2 3 3 -+ 4 2 +3 3 -t 4 2 -t 3 3 -+ 4 2 -+ 3 3 +4 2 -+ 3 3+4 -+
Freq,MHz 27,097.94 36,130.51 27,100.54 36,133.84 27,766.79 37,022.38 27,769.44 37,025.72 24,257.56 32,343.26 24,258.33 32,344.30 24,740.16 32,986.74 24,741.60 32,988.61
'Calculated from v = 2B(J t 1);IBB = 5.05376 X
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I,: ,u.kZ 111.8999 111.9001 111.8891 111.8897 109.2044 109.2044 109.1940 109.1946 125.0025 125.0031 124.9985 124.9991 122.5641 122.5646 122.5570 122.5577 l o 5 MHz
!J A'.
-
Spectra. The frequencies of the J = 2 3 and J = 3 4 transitions of the eight isotopic species studied are listed in Table I. The transitions were measured at low pressures with the absorption cell cooled slightly below room temperature. Klystron sources and oscilloscope display were used with a standard Stark spectrometer. Line widths could not be reduced below about 0.5-1.0 MHz, probably due to unresolved quadrupole coupling. Nevertheless, typically about 10 measurements on a transition were made at different pressures and Stark voltages and a standard deviation of about fO.05 MHz was obtained. Stark voltages sufficient to modulate the K = 0 components were employed. To avoid any systematic errors arising from measurements in different laboratories, we also remeasured the eight transitions for the nitrogen-14 species that we utilized in our calculations. The agreement with Schirdewahn's measurements*was between fO.O1 and k0.08 MHz. The measurements of the other workers9 were less precise and the agreement was typically f0.1-0.3 MHz.13 The dipole moment measurements were made using a precision dc power supply14 (Fluke, Model 412B). The dipole moment of OCSl5 was used to calibrate the Stark septum. Analysis and Discussion Boron-Nitrogen Distance. Ordinarily, the boron-nitrogen distance would be calculated from measurements on three isotopic species-a parent isotopic species and two species in which the boron atom and the nitrogen atom, respectively,were subs#ituted. For example, a set of suitable species would be Me314NsllBH3 (parent), Me315WJlBH3, and Me314NJoBH3. The coordinates of the boron and nitrogen atoms would be calculated from Kraitchman's equations16 which have the form
zs -zp = p z , 2 where ISand I p are moments of inertia of the substituted and parent isotopic species, p is a reduced mass calculated from the known masses,l7 and ZSis the coordinate of the substituted atom in the principal-axis system of the parent isotopic species. Equation 1 can be reliably used to locate an atom on the symmetry axis when it is far from the center of mass. When the substituted atom has a small coordinate (
